4, so sánh A và B:
a,A=\(\dfrac{3}{8^3}+\dfrac{7}{8^4}\);B=\(\dfrac{7}{8^3}+\dfrac{3}{8^4}\)
b,A=\(\dfrac{10^7+5}{10^7-8}\);B=\(\dfrac{10^8+6}{10^8-7}\)
c,A=\(\dfrac{10^{1992}+1}{10^{1991}+1}\);B=\(\dfrac{10^{1993}+1}{10^{1992}+1}\)
Soánh A và B
A=\(\dfrac{8^9+12}{8^9+7}\) và B=\(\dfrac{8^{10}+4}{8^{10}+1}\)
Các bạn giúp với :<
Bài 1:
a, CMR: A = \(\dfrac{3}{1^2.2^2}+\dfrac{5}{2^2.3^2}+\dfrac{7}{3^2.4^2}+...+\dfrac{21}{10^2.11^2}< 1\)
b, Cho B = \(\dfrac{3}{4}+\dfrac{8}{9}+\dfrac{15}{16}+\dfrac{24}{25}+...+\dfrac{2499}{2500}.\) CMR: B không phải là số nguyên.
c, So sánh: C = \(\dfrac{2}{2^1}+\dfrac{3}{2^2}+\dfrac{4}{2^3}+...+\dfrac{2021}{2^{2020}}\) với 3.
CMR : \(\dfrac{2}{5}< A< \dfrac{8}{9}\)
Với \(A=\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+\dfrac{1}{5^2}+\dfrac{1}{6^2}+\dfrac{1}{7^2}+\dfrac{1}{8^2}+\dfrac{1}{9^2}\)
Bài 1: Tính:
a) 10,(3) + 0,(4) - 8,(6)
b) \(\dfrac{0,8:\left(\dfrac{4}{5}.1,25\right)}{0,64-\dfrac{1}{25}}+\dfrac{\left(1,08-\dfrac{2}{25}\right):\dfrac{4}{7}}{\left(6\dfrac{5}{9}-3\dfrac{1}{4}\right).2\dfrac{2}{17}}+\left(1,2.0,5\right):\dfrac{4}{5}\)
1 So sánh
a) \(\dfrac{51}{56}và\dfrac{61}{66}\)
b)\(\dfrac{41}{43}và\dfrac{172}{165}\)
c)\(\dfrac{101}{506}và\dfrac{-707}{3534}\)
d) \(\dfrac{-43}{119}và\dfrac{41}{117}\)
2 Rút gọn và quy đồng
a)\(\dfrac{125}{1000};\dfrac{198}{126};\dfrac{3}{243};\dfrac{103}{3009}\)
b)\(\dfrac{1}{2};\dfrac{1}{3};\dfrac{1}{38};\dfrac{-1}{12}\)
c)\(\dfrac{9}{30};\dfrac{90}{8};\dfrac{15}{1000}\)
3 So sánh
a)\(\dfrac{-3}{5}và\dfrac{39}{65}\)
b)\(\dfrac{-9}{27}và\dfrac{11}{123}\)
c) \(\dfrac{-3}{4}và\dfrac{4}{-5}\)
d)\(\dfrac{2}{-3}và\dfrac{5}{7}\)
Bài 1: Tìm a,b biết:
a, \(\dfrac{a-1}{-2}\) = \(\dfrac{-8}{a-1}\)
b, \(\dfrac{a}{27}\) = \(\dfrac{-5}{9}\) = \(\dfrac{-45}{b}\)
Bài 1: tính
Cho A= \(\dfrac{1}{31}+\dfrac{1}{32}+\dfrac{1}{33}+........+\dfrac{1}{60}>\dfrac{7}{12}\)
B=\(\dfrac{1}{3^2}+\dfrac{1}{3^2}+\dfrac{1}{5^2}+.....+\dfrac{1}{50^2}\)
CMR B > \(\dfrac{1}{4}\); B < \(\dfrac{4}{9}\)
C = \(\dfrac{1}{2}.\dfrac{3}{4}.\dfrac{5}{6}.\dfrac{7}{8}...........\dfrac{79}{80}\)<\(\dfrac{1}{9}\)
cho A=\(\dfrac{1}{2}.\dfrac{3}{4}.\dfrac{5}{6}.\dfrac{7}{8}...\dfrac{79}{80}\)
CMR A<\(\dfrac{1}{9}\)
